1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to improving communication performance.
2. Introduction
A wireless communication network may be deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network.
As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance. To supplement conventional network access points (e.g., macro access points), small-coverage access points may be deployed (e.g., installed in a user's home) to provide more robust indoor wireless coverage or other coverage to mobile units. Such small-coverage access points may be referred to as, for example, femto access points, femto cells, Home NodeBs (HNBs), Home eNodeBs (HeNBs), or access point base stations. Typically, such small-coverage base stations are connected to the Internet and the mobile operator's network via a DSL router or a cable modem.
In practice, there may be a relatively large number of small-coverage access points deployed in a network. Consequently, when an access terminal being paged has moved in idle state, the network could potentially need to send page messages to a large number of access points (e.g. HNBs and HeNBs). However, many of these access points may have restricted access (e.g., comprise closed subscriber group (CSG) cells). Consequently, paging optimization may be employed to avoid sending pages to access points that an access terminal is not authorized to access. For example, the network may only page an access terminal at those access points that are associated with a tracking area identifier (TAI) that is in the access terminal's registered TAI list and that are associated with a CSG identifier (CSG ID) that is in the access terminal's allowed CSG list (e.g., CSG whitelist).
A potential problem with such paging optimization relates to its interaction with the synchronization between the network and the access terminal of CSG subscriber information (e.g., the allowed CSG list). For example, a subscriber may be removed from a CSG, but the access terminal's allowed CSG list may not be updated for some time. If the network is updated and then does not page the access terminal at any access points associated with this CSG, it is possible that the access terminal may be in idle mode at an access point for this CSG and not be reachable for paging. As another example, when a CSG subscription expires, the entry for this CSG in the allowed CSG list of the access point may not immediately be removed. In this case, if the access terminal camps on an access point for this CSG in idle mode prior to determining that the subscription has expired, the access terminal may not be reachable for paging.
An additional potential problem of paging optimization relates to how long the CSG ID of an expired CSG is to be stored in the network (e.g., in a subscription server, a mobility manager, etc). One possible approach is to store the CSG ID until after the CSG ID is removed from the access terminal list (e.g., by an open mobile alliance device management (OMA-DM) update or over the air (OTA) update). However, such an approach requires OMA-DM or OTA to be run to remove the CSG.
As mentioned above, paging optimization may be employed to avoid sending pages to access points where an access terminal is not authorized. One way of achieving this is to include the access terminal's whitelist (e.g., a CSG whitelist) in the page. For example, a mobility manager may use its knowledge of the whitelist to filter the pages that it sends out. Thus, the paging optimization may be optionally performed at the mobility manager. As another example, if an access point gateway is employed (e.g., a HeNB gateway, HeNB-GW), the access point gateway may use the whitelist included in the page to filter the page. Thus, the paging optimization may optionally be performed at an access point gateway. As yet another example, upon receiving a page including a whitelist, an access point may use the whitelist to decide whether or not to transmit the page over the air. Thus, the paging optimization may optionally be performed at the access point. This may be useful if the mobility manager or the access point gateway does not perform any paging optimization. However, there may be a concern that sending a whitelist to an access point may violate security concerns if the access point (e.g., a HeNB) is a customer device.